Special Design---Special double button design with soft TPR material increased friction with the door knob. When you need to open the door,press the double buttons and turn the door knob easily. Easy Installation/Release---No drill and tools need,no harm to the door.Take off the door knob cover then set it on the door knob and close the two covers,the door knob is in lock.It can be easily released by a screwdriver. Why need it---Prevent babies from opening the door and getting into dangers like the toilet or the storeroom and get injured;Prevent babies from going in or out of the house without adults' superision; Prevent children from playing with the door and pinchingtheir fingers. Please note that this product has been updated, with only a little difference in appearance, but no change in function. You may receive products both in old version and the new version, but the function is completely the same, please feel free to purchase.